Recently, it has been proposed to use hydrogen as a clean energy source. Particularly, automobiles powered by fuel cells using hydrogen as fuel are being actively developed. The exhaust gas from fuel cells using hydrogen as fuel does not contain nitrogen oxide, particulate matter (PM), carbon dioxide, etc., which are contained in the exhaust gas from an internal combustion engine, and therefore such fuel cells are suitable as a clean power source which can prevent environmental pollution and global warming.
However, since hydrogen occupies a large volume when stored, a means for feeding hydrogen as a fuel has been problematic, especially for fuel cells for automobiles.
In connection with this problem, as described in Patent Documents 1 and 2 below, a method for generating hydrogen by decomposing ammonia, etc., is attracting attention. For example, Patent Document 1 proposes a hydrogen generating apparatus for fuel cells having a decomposer, which decomposes at least one of ammonia and hydrazine as a hydrogen source into nitrogen and hydrogen by a catalytic reaction, and then supplies the obtained nitrogen and hydrogen to a fuel cell. In one embodiment of the hydrogen generating apparatus for fuel cells, unreacted ammonia and hydrogen in the exhaust gas from fuel cells are combusted by a catalytic reaction in a combustion assembly, and the exhaust gas heat from this combustion assembly is supplied to a decomposer which decomposes ammonia, etc. Patent Document 1 describes that, according to this embodiment, a heat source to heat a decomposer becomes unnecessary and therefore energy efficiency improves.